The Icewind Dale Fixpack is designed to fix several bugs and errors that remain in the game after the official patches have been applied. It works on with or without the expansions Heart of Winter and Trials of the Luremaster installed. In fact, many issues quietly fixed by Heart of Winter or Trials of the Luremaster have been rolled back to every version of the game. This originally started as a component of the IWD Tweak Pack, but was broken out in to its own mod because 1) it's gotten fairly extensive on its own and 2) it should be installed right after the official patches whereas the tweaks should be last installed.